1. Field of the Invention
The present invention relates to a display device. More specifically, the present invention relates to an electron emission display and a driving method thereof.
2. Description of the Related Art
In general, a flat panel display (FPD) is a display device in which a wall is provided between two substrates to manufacture an airtight device, and appropriate elements are arranged in the airtight device to display desired images. The importance of the FPD has been emphasized following the development of multimedia technologies. In response to this trend, various flat type displays such as the liquid crystal display (LCD), the plasma display panel (PDP), and the field emission display (FED) have been put to practical use.
In particular, since an electron emission display uses phosphorous emission caused by electron beams in a like manner of the cathode ray tube (CRT), it has a high probability of realizing a flat-type display which maintains the excellent features of the CRT, provides no image distortion, and allows low power consumption. In particular, it satisfies view angle, high-rate response, high resolution, fineness, and slimness criteria, and accordingly, it has become the center of public attention as the next-generation display.
The above-described electron emission display uses a cold cathode rather than a hot cathode, which includes an FED, an surface conduction emitting display (SED), and an metal insulator metal (MIM) display.
FIG. 1 shows a cross-sectional view of an electron emission display. As shown, the electron emission display includes a rear substrate 11 and a front substrate 12. A cathode electrode 13 and a gate electrode 17 are formed with an insulation layer 16 therebetween on the rear substrate 11. An emitter 15 for emitting electrons according to the voltage applied to the cathode electrode 13 and the gate electrode 17 is formed on the cathode electrode 13.
The front substrate 12 is formed to face the rear substrate 11, and an anode electrode 14 for pulling the electrons output from the emitter 15 is formed on the front substrate 12. Also, a phosphor surface 19 of red, green, and blue phosphors for the pulled electrons to collide with and emit light is formed on the anode electrode 14.
A focusing electrode 18 is formed between the rear substrate 11 and the front substrate 12, and it focuses the electrons generated by the emitter 15 formed on the cathode electrode 13 so that the electrons may reach the desired phosphor surface 19. Further, a spacer 20 for dividing the anode electrode 14 and the focusing electrode 18 is used.
The above-configured electron emission display concentrates high fields on the emitter 15 to emit the electrons according to the quantum-mechanical tunnel effect, and the electrons emitted from the emitter 15 are accelerated by the voltage applied between the cathode electrode 13 (a scan electrode) and the gate electrode 17 (a data electrode) and collide with the phosphor surface 19 formed on the anode electrode 14, thereby emitting the light and displaying images.
The brightness of the images displayed when the emitted electrons collide with the phosphor surface 19 varies according to values of input digital video signals. In more detail, the values of the digital video signals have 8-bit RGB data. That is, the values of the digital video signals cover 0 (00000000(2)) to 255 (11111111(2)). 256 gray scales are represented by the 256 values, and the brightness of colors are represented by the digital values.
However, since the DC voltage is consecutively applied to the focusing electrode 18 in the conventional electron emission display, part of the electrons emitted from the emitter 15 are not provided to the anode electrode 14 but rather to the focusing electrode 18 or the spacer 20, and they charge the focusing electrode 18 or the spacer 20. As a result, the electrons charged in the focusing electrode 18 or the spacer 20 influence the emitted electrons around the spacer 20, and hence, the electron beams are bent, and the images around the spacer 20 and the focusing electrode 18 are distorted.